Volcanic unrest continues at Okmok Volcano. Satellite data from Monday, August 18, indicated intermittent small ash emissions which drifted generally to the south and reached no higher than 10,000 to 15,000 feet. Beginning Tuesday, August 19, the level of seismic activity approached pre-eruption levels and satellite data showed that ash was no longer being emitted. Despite mostly cloudy conditions on Thursday, August 21, satellite observations show a possible thermal anomaly at the volcano. Seismic activity stayed near pre-eruption levels the remainder of the week.

Although the level of seismicity has declined and it appears that ash is no longer being erupted, it is possible for vigorous ash emissions to resume at any time.

Seismic activity at Kasatochi continues. Earthquakes were detected by the AVO seismic network on Great Sitkin Island 25 miles west of Kasatochi all week. Satellite views the majority of the week were obscured by clouds. On Sunday, August 17, people on Adak reported smelling sulfur and on Monday, August 18, clear satellite views showed a steam plume from the volcano's summit.

The volcano remains in a restless condition and is still considered hazardous to approach. Further explosive eruptive activity remains possible.

Clouds have obscured the volcano in satellite views most of the week. Partly cloudy satellite views on Tuesday, August 19 showed a weak thermal anomaly at Cleveland volcano and no plume was observed. AVO has received no additional information about activity at Cleveland this week.

Small ash bursts and low-level ash plumes may resume at the volcano. It is also possible for larger, higher reaching plumes to be produced without warning.

OTHER ALASKA VOLCANOES

Seismic activity is monitored in real time at 30 volcanoes in Alaska. Satellite images of all Alaskan volcanoes are analyzed daily for evidence of ash plumes and elevated surface temperatures. Some volcanoes may currently display anomalous behavior but are not considered to be at a dangerous level of unrest. Augustine, Iliamna, Redoubt, Wrangell, Gareloi, Great Sitkin, Makushin, Fisher, Shishaldin, Isanotski, Pavlof, Veniaminof, Ugashik-Peulik, Griggs, Snowy, Fourpeaked, Aniakchak, Tanaga, Kanaga, Akutan, Westdahl, Dutton, Ukinrek Maars, Martin, Mageik, Trident, Katmai, Novarupta, Spurr, and Korovin volcanoes are in color code GREEN and volcano alert level Normal. All are at or near normal levels of background seismicity. AVO did not detect ash plumes or significant elevated surface temperatures in the vicinity of any volcano.

The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.

VOLCANO ALERT LEVELS

NORMALVolcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.

ADVISORYVolcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.

WATCHVolcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway but poses limited hazards.

WARNINGHazardous eruption is imminent, underway, or suspected.

AVIATION COLOR CODES

GREENVolcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.

YELLOWVolcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.

ORANGEVolcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway with no or minor volcanic-ash emissions [ash-plume height specified, if possible].

REDEruption is imminent with significant emission of volcanic ash into the atmosphere likely OR eruption is underway or suspected with significant emission of volcanic ash into the atmosphere [ash-plume height specified, if possible].